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Sep 19, 2013
09/13

by
Kim Bostroem; Timo Felbinger

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A novel secure communication protocol is presented, based on an entangled pair of qubits and allowing asymptotically secure key distribution and quasi-secure direct communication. Since the information is transferred in a deterministic manner, no qubits have to be discarded. The transmission of information is instantaneous, i.e. the information can be decoded during the transmission. The security against arbitrary eavesdropping attacks is provided. In case of eavesdropping attacks with full...

Source: http://arxiv.org/abs/quant-ph/0209040v2

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Sep 18, 2013
09/13

by
Kim Bostroem; Timo Felbinger

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In order to compress quantum messages without loss of information it is necessary to allow the length of the encoded messages to vary. We develop a general framework for variable-length quantum messages in close analogy to the classical case and show that lossless compression is only possible if the message to be compressed is known to the sender. The lossless compression of an ensemble of messages is bounded from below by its von-Neumann entropy. We show that it is possible to reduce the...

Source: http://arxiv.org/abs/quant-ph/0105026v2

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Sep 18, 2013
09/13

by
Timo Felbinger; Martin Wilkens

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We propose an optimized algorithm for the numerical simulation of two-time correlation functions by means of stochastic wave functions. As a first application, we investigate the two-time correlation function of a nonlinear optical parametric oscillator.

Source: http://arxiv.org/abs/quant-ph/9903089v1

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Sep 19, 2013
09/13

by
Kim Bostroem; Timo Felbinger

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We briefly review the security of the ping-pong protocol in light of several attack scenarios suggested by various authors since the proposal of the protocol. We refute one recent attack on an ideal quantum channel, and show that a recent claim of falseness of our original security proof is erroneous.

Source: http://arxiv.org/abs/0708.2986v2

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Jul 20, 2013
07/13

by
H. Hoffmann; K. Bostroem; T. Felbinger

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In the paper [Phys. Rev. A \textbf{69}, 052319 (2004)], a quantum direct communication protocol is proposed which is claimed to be unconditionally secure even for the case of a noisy channel. We show that this is not the case by giving an undetectable attack scheme.

Source: http://arxiv.org/abs/quant-ph/0406115v1

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Sep 22, 2013
09/13

by
T. Felbinger; L. Santos; M. Wilkens; M. Lewenstein

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We analyze the multi-time correlations of a laser-induced Bose-Einstein condensate. We use quantum stochastic methods to obtain under certain circumstances a Fokker-Planck equation which describes the phase-difussion process, and obtain an analytical expression of the two-time correlations. We perform also quantum Monte Carlo numerical simulations of the correlations, which are in good agreement with the predicted analytical results.

Source: http://arxiv.org/abs/cond-mat/0001382v1

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Sep 21, 2013
09/13

by
J. Eisert; T. Felbinger; P. Papadopoulos; M. B. Plenio; M. Wilkens

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We establish a quantitative connection between the amount of lost classical information about a quantum state and the concomitant loss of entanglement. Using methods that have been developed for the optimal purification of mixed states we find a class of mixed states with known distillable entanglement. These results can be used to determine the quantum capacity of a quantum channel which randomizes the order of transmitted signals.

Source: http://arxiv.org/abs/quant-ph/9907021v2